1. Field of the Invention
The invention relates to a transmission system for a vehicle, such as a straddle type vehicle or the like. More particularly, the invention relates to various types of transmission systems that function automatically or semi-automatically.
2. Description of Related Art
Internal combustion engines generally installed in vehicles, such as rider mounted or straddle type vehicles or the like, develop their power output at high speeds of rotation. It is therefore necessary to reduce the speed between the crankshaft and the shaft that drives the wheels. However, the torque that the engine delivers can be varied only within narrow limits. For this reason, it is necessary to be able to alter the transmission ratio, so that the driving forces applied to the wheels of the vehicle can be adapted to varying road resistance conditions.
The speed reduction can be obtained by means of a transmission (change-speed gearbox) interposed between a clutch and a final drive. Such a transmission alters the torque that is transmitted. The transmission may include a main shaft, a secondary shaft and an output shaft (connected to the wheels). A multiple disk transmission clutch may be mounted on one end of the main shaft and a dog clutch body, or shift fork, may be slidably mounted on a shaft for changing the transmission gear ratio.
When an operator wants to start a straddle type vehicle with a manual transmission, he or she has to increase the speed of the engine, gradually depress a clutch lever and move a toe shift pedal to engage the first gear train of the transmission. Having the first speed gear train engaged and increasing the speed, the operator has to depress the clutch lever to disengage the transmission clutch and move the toe shift pedal to change the transmission gear ratio of the engine. Because operation of the clutch lever or toe shift pedal may be disagreeable or difficult, some prior transmission systems have been developed wherein the clutch lever is not present or operation of the toe shift pedal is eased.
U.S. Pat. No. 3,894,442 discloses a semi-automatic gear shifting apparatus for shifting gears in a gear box of a motorcycle. The gears are shifted by rotating a spindle. The spindle is operably connected to a ratchet-type gear shifting means. A lever arm is connected at one end to the spindle and is connected at its other end to a toe pedal of a motorcycle by means of a mounting bracket. A solenoid connecting rod is operably connected to a core of the solenoid. The rod is operably connected at one end to the toe pedal. The rod is thus reciprocated to move the lever arm and the spindle by the solenoid, which is actuated by a pair of push button switches connected to an electrical power source. The spindle is rotated through a relatively small arc. The degrees of the arc are determined by the distance the ratchet is required to move to effect a change in the gears in the gear box.
The semi-automatic gear shifting apparatus is activated when energized selectively through the switches. Each time the apparatus is activated one gear shifting cycle is completed. When the apparatus is de-activated, the lever arm is returned to the neutral position. The use of a gear disengaging clutch (and a clutch lever) is not required here because the movement of the shifting lever arm is sufficiently rapid so as to not damage the gear while effecting the gear shift.
However, experience has shown that under certain operating conditions, the movement of the shifting lever arm may be difficult, and a very powerful solenoid is thus required. Moreover, having an exposed solenoid mounted on the engine may be hazardous because its operation may be jeopardized by roadway debris or impediments during driving.
U.S. Pat. No. 5,299,652 discloses a handlebar control system for a motorcycle that enables control of a motorcycle without moving the hands from the handlebars. A shift switch with an up-shift button and a down-shift button is provided on a right handlebar while the left handlebar has a normal clutch lever mounted thereon. An advanced shift arm is connected at one end to a shift rod while the other end is connected to an actuator, whereby, in operation, the actuator causes movement of the shift arm to change the transmission gear ratio. The system also comprises an air compressor that maintains an operating pressure of about 100 p.s.i., a tank, a pneumatic line, an up-shift control solenoid, a down-shift control solenoid and an electric circuit connected to a twelve volt battery.
In operation, an operator depresses the clutch lever and then the up-shift button, which causes the up-shift control solenoid to open to permit a burst of air to flow to the actuator to change the transmission gear ratio. Down-shifting occurs by pushing the down-shift button. The system may also comprise an optional pneumatic stop switch for operating the transmission without using the clutch lever. However, this system requires a lot of space and is not adapted to be mounted in a restrictive area. Moreover, having an exposed actuator may be hazardous because its operation may be jeopardized by roadway debris during driving.
However, prior art semi-automatic transmissions installed on a straddle type vehicle have some inconveniences, such as requiring the operation of a shift toe pedal. This operation may be difficult because an important effort is required from the operator when the temperature is below a certain point. Also, for an operator who wears large boots, operation of a shift toe pedal may be complicated. Thus, it would be beneficial to eliminate a shift toe pedal to result in a more user-friendly transmission system.
Additionally, prior art semi-automatic and automatic transmissions typically either forego the use of the clutch or re-engage the clutch very abruptly subsequent to gear shift. Accordingly, these transmissions shift very roughly, thereby decreasing rider comfort and, perhaps causing undue wear on the transmission componentry. There is thus a need in the art to provide a semi-automatic or automatic transmission that is capable of shifting smoothly.
Furthermore, semi-automatic and automatic transmissions have lacked an ability to adjust the aggressiveness of shifting. In particular, the shift commands with which the transmission controller initiates gear shifting has been based on, either directly or indirectly, engine speed. Therefore, no matter the operating conditions of the vehicle at that time, the controller shifts gears when the predetermined engine speed is obtained. Accordingly, these systems may cause erratic or inconvenient shift changes. There is thus a need in the art to provide a semi-automatic or automatic transmission with the ability to determine or otherwise realize the current operating conditions of the vehicle and provide responsive shift changes.
One aspect of embodiments of the invention is to provide a semi-automatic or automatic transmission that allows the operator to adjust the operating parameters.
Another aspect of embodiments of the invention is to provide a semi-automatic or automatic transmission that is capable of smoothly shifting gears.
Another aspect of embodiments of the invention is to provide a semi-automatic or automatic transmission that is capable of realizing operating conditions of the vehicle and providing responsive shift changes.
In accordance with this invention an automatic transmission assembly is provided that comprises an engine with a crankshaft that rotates at a speed and a transmission operatively connected to the crankshaft. The transmission includes a main shaft, an output shaft, a plurality of speed gear trains disposed between the main shaft and the output shaft, a gear shifter selectively connected to one of the speed gear trains that causes the selected gear train to engage the output shaft, and a clutch device connected to the main shaft that selectively disengages the main shaft from the crankshaft to permit shifting between the speed gear trains. Driving torque is transmitted from the crankshaft to the main shaft and through the selected speed gear train to the output shaft. A shifting mode selector selects between plural modes of shifting operation. A controller is provided in communication with the shifting mode selector, the clutch device and the gear shifter that controls the clutch device to engage and disengage the main shaft from the crankshaft and controls the gear shifter to select one of the plurality of speed gear trains based on a selected shifting mode. The controller includes an input connected to the engine, an output connected to the clutch device and the gear shifter, and a memory in which a plurality of sets of values are stored that control gear change shifting based on sensed operating conditions, wherein each set of values corresponds to a different shifting mode.
Also in accordance with this invention a method is provided of controlling automatic shifting of a transmission associated with an engine that provides torque, wherein the transmission includes a clutch, a plurality of speed gear trains, and a gear shifter. The method includes selecting a shifting mode from a plurality of modes each based on different engine operating conditions, sensing engine operating conditions, comparing sensed engine operating conditions to stored, predetermined engine conditions in the selected mode to determine when shifting will occur, operating the clutch to disengage torque transmission to permit shifting, operating the gear shifter to select a speed gear train, and operating the clutch to engage torque transmission to the speed gear train.
The invention can also be embodied in a recording medium that stores a control program for controlling a transmission having a clutch and a gear shifter. The recording medium includes instructions for causing the transmission to select a shifting mode from a plurality of modes each based on different engine operating conditions, sense engine operating conditions, compare sensed engine operating conditions to stored, predetermined engine conditions in the selected mode to determine when shifting will occur, operate the clutch to disengage torque transmission to permit shifting, operate the gear shifter to select a speed gear train, and operate the clutch to engage torque transmission to the speed gear train.
Another feature of this invention relates to an automatic transmission assembly comprising an engine with a crankshaft that rotates at a speed and a transmission operatively connected to the crankshaft. The transmission includes a main shaft, an output shaft, a plurality of speed gear trains disposed between the main shaft and the output shaft, a gear shifter selectively connected to one of the speed gear trains that causes the selected gear train to engage the output shaft, a clutch device connected to the main shaft that selectively disengages the main shaft from the crankshaft to permit shifting between the speed gear trains, and a clutch actuator connected to the clutch to actuate clutching action. Driving torque is transmitted from the crankshaft to the main shaft and through the selected speed gear train to the output shaft. A controller is provided in communication with the clutch actuator and the gear shifter that controls the clutch actuator to cause the clutch device to engage and disengage the main shaft from the crankshaft and controls the gear shifter to select one of the plurality of speed gear trains based on a selected shifting mode. The controller includes an input connected to the engine, an output connected to the clutch actuator and the gear shifter, and a memory in which a plurality of sets of values are stored that modulate the clutch actuator to control the clutch device based on sensed operating conditions.
The invention also includes a method of modulating shifting in a transmission including a clutch and a clutch actuator, comprising sensing engine operating conditions, comparing sensed engine operating conditions to stored, predetermined engine conditions to determine a modulation value for the clutch actuator, operating the clutch to disengage torque transmission to permit shifting, operating the gear shifter to select a speed gear train, and operating the clutch to engage torque transmission to the speed gear train based on the modulation value, wherein the clutch engages the torque transmission with a predetermined delay based on the modulation value.
The invention can be embodied as a recording medium that stores a control program for controlling shifting in a transmission having a clutch, a clutch actuator and a gear shifter. The recording medium including instructions for causing the transmission to sense engine operating conditions, compare sensed engine operating conditions to stored, predetermined engine conditions to determine a modulation value for the clutch actuator, operate the clutch to disengage torque transmission to permit shifting, operate the gear shifter to select a speed gear train, and operate the clutch to engage torque transmission to the speed gear train based on the modulation value, wherein the clutch engages the torque transmission with a predetermined delay based on the modulation value.
The assemblies, methods and recording mediums embodied herein can be used in combination with various types of vehicles, including for example, a straddle type vehicle.
Other aspects, objects and features of the invention will become apparent by reference to the following specification and to the drawings.